The progressive strategy of investigating President Donald Trump nonstop for Russian collusion or obstruction of justice or witness tampering so far has produced no substantial evidence of wrongdoing.

The alternate strategy of derailing the new administration before it really gets started hasn’t succeeded either, despite serial efforts to sue over election results, alter the Electoral College vote, boycott the inauguration, delay the confirmation of appointments, demand recusals, promise Trump’s impeachment or removal through the 25th Amendment, and file suit under the Emoluments Clause.

A third strategy of portraying Trump as a veritable monster likewise so far has failed in four special elections for House seats.

Apparently progressives have accepted the idea that Barack Obama’s formula of twice winning the Electoral College is not yet transferrable to other progressive candidates such as Hillary Clinton. And they probably have concluded that Obama’s progressive political agenda proved unpopular with voters by 2010 and had to be implemented by ad hoc executive orders — presidential prerogatives now utilized by Donald Trump to overturn the ones Obama issued.

A fourth potential pathway to power would be a return to Bill Clinton’s pragmatic agendas of the 1990s. But apparently progressives find that centrist remedy worse than the malady of losing elections — given that during the Obama tenure, more than 1,000 state and local offices were lost to Republicans, in addition to majorities in the House and Senate, and a majority of governorships and legislatures.

What next?

Trump acts as if he is a Nietzschean figure, assuming that anything that does not destroy him only makes him stronger. And now, slowly, his accusers are becoming the accused.

One nagging problem with the progressive case against Trump for purported Russian collusion and obstruction of justice was that members of the Obama administration had more exposure to those allegations than did the political newcomer Trump.

Last year, then-FBI Director James Comey testified that not only did former Attorney General Loretta Lynch improperly meet in secret with Bill Clinton during an investigation of Hillary Clinton, but that Lynch had asked Comey to downplay the investigation into Hillary’s use of a private email server during her tenure as secretary of state. Comey confessed that he had reluctantly agreed to Lynch’s request.

Earlier this month, in testimony before the Senate Intelligence Committee, Comey admitted that he asked a friend to leak notes about Comey’s earlier conversation with Trump in hopes of forcing the nomination of a special investigator to lead the Russia investigation — perhaps a successful gambit, given that Comey’s friend, former FBI Director Robert Mueller, was soon appointed to that role.

Comey also wrongly dismissed Hillary Clinton’s email problems because of a perceived lack of criminal intent — a supposedly mitigating circumstance that legally should have had no bearing on things.

As far as alleged Russian collusion, there had long been conservative accusations that Bill and Hillary Clinton used Hillary’s status as secretary of state to leverage honoraria for Bill and donations to the Clinton Foundation in exchange for concessions to Russian interests.

Moreover, Russian tampering efforts had been going on for months before the 2016 election, but without any retaliatory measures from the Obama administration, which knew about Russia’s meddling.

In an inadvertent hot-mic request in 2012, Obama asked outgoing Russian President Dmitry Medvedev to urge Russian President Vladimir Putin “to give me space” during Obama’s re-election campaign, so that after his assumed success, Obama could reciprocate with “more flexibility” on Russian issues. In the present highly charged climate, would that be seen as a form of Russian collusion?

Meanwhile, the House Intelligence Committee is still investigating whether top Obama administration officials wrongfully used the power of foreign-intelligence collection to conduct surveillance of Americans — particularly members of the Trump campaign.

The point is not whether the Clintons, James Comey, Barack Obama or members of the Obama administration can be proven to have engaged in illegal or unscrupulous behavior.

Rather, the lesson is that progressives should have offered alternative political visions that might have won back the American people rather than attempting to terminate the Trump presidency on charges to which the progressive side was far more vulnerable.

Now that Trump is emerging from successful House special elections and has fended off six months of media attacks, celebrity invective and progressive efforts to abort his tenure, he seems to be going back on the offensive.

Currently, House and Senate investigations are doing to Democrats what has been done Trump. So far these probes seem to have better chances to prove alleged wrongdoing.

What does all this political back-and-forth mean?

Democrats struck preemptively to take out Trump before he unwound the Obama legacy. That effort has probably been stalled.

The return volley is being launched at a time when an energized Trump is gaining momentum on health care and tax reform, and an improving economy.

In sum, to thwart a new president’s policies, it is probably wiser to offer alternative agendas instead of trying to destroy him before he has even entered office.

Victor Davis Hanson is a classicist and historian at the Hoover Institution, Stanford University and the author, most recently, of “The Father of Us All: War and History, Ancient and Modern” You can reach him by emailing author@victorhanson.com.